Groundwater forms the invisible, subsurface part of the hydrological cycle, playing a vital role for maintaining base flows of rivers during the dry seasons. It is also a vital source of water for modern economies, accounting for 25% of total water extraction worldwide and a quarter of the irrigation water used to grow the world's food (Aquastat, 2016). Yet, aquifers are being over-exploited at an alarming rate in many regions around the world-a situation that is expected to worsen under climate change as recharge rates will be increasingly affected (Famiglietti, 2014;Taylor et al., 2013). Groundwater depletion contributes to the decisions by water managers to "close" access to water resources in aquifers and river basins (Molle et al., 2010). As societal and environmental needs cannot be met for at least part of the year, water managers must deal with complex trade-offs between economic interests, livelihoods, and environmental priorities.To tackle overexploitation, groundwater management is progressively shifting from an open-access regime of water resource extraction to one of regulated access all over the world (Giordano et al., 2009;Shah, 2009). Regulated access typically relies on setting a sustainable flow rate or volumetric cap on total water extraction, and reducing and maintaining extractions at or below that cap (Rinaudo et al., 2020). It can also rely on a pigouvian tax or restrictions imposed when sustainability limits are reached (for example, groundwater threshold levels). The core issue when closing access to water resources becomes how to best allocate limited water supplies between competing users, and between users and the environment. It involves setting up processes and mechanisms which enable social actors to share water according to a recognized set of values and priorities.Much academic debate has focused on the question of who should control or supervise allocation decision-making, with no conclusive outcome as to whether state or community approaches are preferable (Bruns et al., 2005;Rinaudo et al., 2019). On the one hand, state approaches appear more accountable, but they have usually failed to effectively reduce groundwater use to sustainable levels (Molle & Closas, 2020b). On the other hand, community approaches appear more legitimate, at least to the regulated. They have been most effective where the community had a social basis for collective action, for example a common

ABSTRACT. To address increasing conflicts between surface water and groundwater users, the state of Nebraska has adopted a more localized and integrated approach in managing water resources. Integrated approaches offer promise in better managing connected water resources within the state; however, little review of the potential benefits and/or challenges of these actions has been conducted. This case study uses both qualitative and quantitative data collection efforts to take an in-depth look at how this new and innovative management system is working through the eyes of stakeholders living and working in the basin. Data collection reveals that overall the current water management system is working relatively well, even though it is still in its infancy. However, the system could be further improved by ensuring all that stakeholder interests are represented, providing increased opportunities to participate, and continuing to work toward more holistic and proactive water management.Key Words: common pool resources; governance; integrated water resources management; mixed-methods research INTRODUCTIONWithin Nebraska, increasing demands for water resources, emerging conflicts between water users, mounting concerns over threatened and endangered species, and obligations to abide by interstate water allocation agreements have motivated the state to revisit traditional approaches toward water management. Consequently, Nebraska's water institutions, which we define as both the formal and informal practices that structure human interactions, including established rules, laws, organizational entities, norms, and codes of conduct (Armitage et al. 2007), have undergone significant change over the past several decades. Nebraska's water institutions have evolved from a system of statecontrolled water resources to a system of divided state and local control, and finally, in certain situations, to a more integrated system of shared state and local control. This recently developed governance structure, which is unique to Nebraska, takes a new and innovative approach to how water resources are managed. However, although more localized and integrated water management approaches offer promise in better managing interconnected water resources, little review of how the current system is actually working exists.

In 2014, the California State Legislature enacted the Sustainable Groundwater Management Act (SGMA), which requires the formation of new local agencies, known as Groundwater Sustainability Agencies (GSAs), to sustainably manage groundwater basins throughout the state. The statute represents the first statewide framework for groundwater management in California. Among other tasks, GSAs, especially those in overdrafted basins, will have to allocate available water among users and set up systems to hold pumpers to their allocated limit. However, SGMA did not change the longstanding framework of groundwater pumping rights established by California courts. This sets up the possibility of conflict between groundwater allocation plans adopted by GSAs and water rights.This Article analyzes the relationship between SGMA and water rights under the common law. It identifies a path for GSAs to allocate groundwater and limit pumping in a manner best situated to sustain judicial scrutiny. We examine how the common law defines water right priorities for groundwater pumping allocations, as well as areas where the common law provides flexibility. This flexibility allows for creativity in arriving at allocations that fit stakeholders' goals for both sustainable and smart water management. We seek to help GSAs reduce the risk of litigation and increase the likelihood their Groundwater Sustainability Plan (GSP) will survive litigation, without judicial modification. There are considerable measures GSAs can take to manage their litigation risk and enhance the durability of their GSPs, including making groundwater allocations in their GSPs consistent with the principles of water rights and seeking consensus among affected stakeholders. We also seek to provide a framework for courts to work out the appropriate relationship between SGMA and the common law of water rights when litigation occurs.

The book brings together a range of leading scholars and practitioners to compile an international account of water allocation policies supporting a transition to sustainable water use in regions where agriculture is the dominant water use. In Section 1, the collection canvasses five key crosscutting issues shaping the challenge of sustainable water allocation policy, such as legal and economic perspectives, the role of politics, the contributions of engineering and technology, the setting of environmental flows, and the importance of indigenous rights. Section 2 presents 16 national, state and transboundary case studies of water allocation policy, covering cases from Europe, the Americas, Central Asia, the Middle East and the Pacific region. These case studies highlight novel and innovative elements of water allocation regimes, which respond to the cross-cutting issues addressed in Section 1, as well as local challenges and social and environmental imperatives. The book provides a comprehensive account of water allocation in a range of international settings and provides a reference point for practitioners and scholars worldwide wishing to draw on the latest advances on how to design and implement sustainable water allocation systems. ISBN: 9781789062779 (print) ISBN: 9781789062786 (eBook) ISBN: 9781789062793 (ePUB)

The state of Nebraska, USA employs a localized, integrated approach to managing water resources to address escalating quantity challenges. Here, we assess differences between agricultural water users' perceptions of water management in a water-stressed area of Nebraska after a first round of water management planning and perceptions of three other stakeholder groups in Nebraska immediately after a second round of water management planning. We also demonstrate the value of augmenting Ostrom's commonpool resource management design principles with locally relevant criteria to evaluate water management at regional and statewide governance scales. Data from a survey of Platte River basin agricultural producers in 2012 were combined with survey data collected in 2019 from Platte basin agricultural producers, Platte basin non-farm residents, and non-farm residents across Nebraska. There were significant increases from 2012 to 2019 in Platte basin producers' perceptions of four criteria and significant decreases in their perceptions of four other criteria. The current system continues to work relatively well, but notable exceptions endure, including a significant decrease in the number of agricultural producers who agree that there is equitable treatment of water users and trust in water management agencies. Non-farm respondents were significantly less likely than producers to agree that the current water management system is working well with regard to enforcing water-use rules.